DoorBird D2101KV surface mounting housing (backbox) Add this to your D2101KV to allow it to be surface mounted. Perfect for retro-fits. 2 finishes available to match your Doorbird: V2A Stainless Steel is IP65, V4A Stainless Steel is IP65 with chrome-nickel steel with molybdenum additive for harsh conditions and is Salt-Water resistant.